In diesel and gasoline engines, air is drawn into a combustion chamber during an intake stroke by opening one or more intake valves. Then, during the subsequent compression stroke, the intake valves may be closed, and a reciprocating piston of the combustion chamber compresses the gases admitted during the intake stroke, increasing the temperature of the gases in the combustion chamber. Fuel is then injected into the hot, compressed gas mixture in the combustion chamber, resulting in combustion of the fuel. In a diesel engine, the fuel may combust with the air in the combustion chamber due to the high temperature of the air, and may not be ignited via a spark plug as in a gasoline engine. The combusting air-fuel mixture pushes on the piston, driving motion of the piston, which is then converted into rotational energy of a crankshaft.
Diesel and/or gasoline fuels may not mix evenly with the air in the combustion chamber, which may lead to the formation of dense fuel pockets. These dense regions of fuel may produce soot (e.g., unburned fuel). Particulate filters may be arranged in an exhaust passage to decrease an amount of soot and other particulate matter from vehicle emissions. However, particulate filters may lead to increased manufacturing costs and may not solve fuel economy issues associated with unburned fuel.
Modern technologies for combating engine soot output may include features for entraining air with the fuel prior to injection. One or more passages may be arranged in the injector body, either as an insert in the engine head deck surface or in the engine head. Air from the combustion chamber may mix with the fuel, thereby cooling the injection temperature while simultaneously entraining air with fuel. A lift-off length may be lengthened and start of combustion may be retarded, thereby limiting soot production through a range of engine operating conditions, reducing the need for a particulate filter.
However, the inventors herein have recognized potential issues with such injectors. As one example, the previously described fuel injectors may no longer sufficiently prevent soot production to a desired level in light of increasingly stringent emissions standards. As such, particulate filters may be located in an exhaust passage, thereby increasing a manufacturing cost and packaging restraint of the vehicle.
In one example, the issues described above may be addressed by a system comprising a fuel injector comprising an egg-shaped nozzle, wherein an opening is shaped to admit combustion chamber gases into a hollow interior of the egg-shaped nozzle forming an annular venturi passage between it and an outlet surface of the fuel injector. In this way, a compact mixer may promote air-fuel mixing prior to injecting the fuel into the combustion chamber.
As one example, the egg shaped nozzle comprises the opening to admit combustion chamber gases. The opening may be a first opening, wherein the egg-shaped nozzle further comprises at least one second opening for expelling the combustion chamber gases to the annular venturi passage. The annular venturi passage may receive fuel directly from a sac of the fuel injector, it may additionally receive fuel from one or more outlet passage extending through an injector body, wherein the outlet passage fluidly couple the sac to a constricted portion of the annular venturi passage. By doing this, the combustion chamber gases in the egg-shaped nozzle and the fuel from the outlet passage may promote a swirling effect in the annular venturi passage to further promote air-fuel mixing.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.